Device structures and device materials to realize low-loss semiconductor devices are desirable. By using, for example, silicon carbide (SiC) as the material, it is possible to design with a lower on-resistance and a higher breakdown voltage than when silicon (Si) is used. There are cases where dislocations called basal plane dislocations (BPDs) exist inside the semiconductor substrate. It is known that the dislocations extend during the device operation particularly in a bipolar mode; characteristic fluctuation of the device occurs; and the loss increases. Because the extension of the dislocations reduces the long-term reliability of the device, it is necessary to suppress the characteristic fluctuation of the semiconductor device recited above.